docs(installation): frame Python as a first-class third script type

Address review feedback: update the section heading and intro so Python
is presented as a first-class script type alongside Shell and PowerShell,
matching the added --script py example and python/ variant directory.

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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jawwad-ali

docs/installation.md

@@ -77,9 +77,9 @@ specify init <project_name> --integration pi
 specify init <project_name> --integration omp
 ```
 
-### Specify Script Type (Shell vs PowerShell)
+### Specify Script Type (Shell, PowerShell, or Python)
 
-All automation scripts now have both Bash (`.sh`) and PowerShell (`.ps1`) variants.
+Automation scripts are available as Bash (`.sh`), PowerShell (`.ps1`), and Python (`.py`) variants.
 
 Auto behavior: